The proposed research will utilize regional and international committees to construct a cooperative glossary of epidemiologic terms, sponsored by the International Epidemiologic Association. This glossary is designed to unify terminology currently being used in the field, and to provide a comprehensive compendium of definitions of epidemiologic terms for reference by workers in the field and in related fields. At present, the collection of terms being used in the field has profilerated to the point that a number of terms are frequently used for a single concept, and vice versa. The glossary will provide a forum for decision-making by a representative body of individuals in the field. The initial proposed collection and grouping of terms to be defined will be carried out by the investigators, and revisions will be made by a committee composed of members from North American institutions. Definitions of terms will be initially drafted by the investigators and will be revised by the North American committee. The final draft of the North American committee will then be submitted to an international committee of International Epidemiological Association regional representatives, who will review the definitions. Those for which a majority of regional representatives suggest a change will be revised, and a vote taken on suggested definitions. Checks will then be carried out by the prinicpal investigators to ensure that no internal inconsistencies among definitions exists. An index will then be prepared. The resulting glossary will represent a first edition, and it is expected that periodic updatings will occur under the auspices of the IEA.